The present invention relates to systems for controlling vapor lock in fuel lines of vehicles employing a Positive pressure circulating fuel supply to the engine. Fuel systems of this type are employed in automotive vehicles having fuel injected engines wherein a fuel pump is provided at the tank for circulating a continuous flow of fuel under positive pressure to the fuel injectors.
In service of vehicles employing injected engines with a positively pressurized flow of fuel continuously circulated to the injectors during engine operation, the fuel lines absorb heat from the engine compartment and problems have been encountered with vapor lock in the fuel line, particularly on the portion of the line returning fuel to the tank. The fuel returning to the tank in a Positively pressurized pumping system is discharged to the tank at substantially atmospheric pressure and therefore the fuel in the return portion of the line is subject to evaporation at a lower temperature than the fuel at a higher pressure when discharged from the pump.
In order to eliminate evaporation and vapor lock of the fuel in the return line, it has been proposed to provide an inter-cooler in the return portion of the fuel line to lower the temperature of the fuel below its vaporization point. One technique that has been suggested is that of providing a heat exchanger with the refrigerant employed for the vehicle air conditioning system. The vehicle air conditioning refrigerant is a convenient source of cooling medium in as much as the air conditioning system is usually operated in climatic conditions which would raise the engine compartment temperatures sufficient to cause vapor lock in the fuel line.
However, in attempting to provide heat exchange between the fuel line and the air conditioning system refrigerant, problems have been encountered because the air conditioning system controls are designed to control flow of refrigerant to provide a slight amount of superheat at the outlet of the air conditioning evaporator; and, therefore little cooling is available in the refrigerant for heat exchange with the fuel line. Accordingly, it has been desired to find a way or means of utilizing a heat exchanger in the air conditioning refrigerant line to cool the fuel line in order to prevent vapor lock in the low pressure side of the fuel line returning to the fuel tank.